The present invention relates generally to hollow core doors and more specifically to an expandable core structure inserted within the interior of the door to provide support for the skins of the door.
Hollow core doors are commonly used in many types of buildings. The common structure of a hollow core door includes a pair of door skins which are separated by a wood frame. The wood frame has vertical wood stiles joined to upper and lower horizontal wood rails. The wood stiles and rails form the edges of the door. A lock block may also be included in the area of the door where locks and handles are attached. A hollow area is enclosed between the two door skins and within the frame. The hollow area typically requires some type of structural reinforcement.
One type of reinforcement commonly used in hollow core doors is a honeycomb core structure that is glued in place between the door skins. The honeycomb core structure may be, for example, corrugated board. The honeycomb structure is supplied in an unexpanded manner. The honeycomb core is stretched across the skin of the interior of the door. One problem with using such a honeycomb core structure is that it is difficult to stretch to achieve an even honeycomb pattern within the door. Commonly, the honeycomb core must be overstretched and then manipulated into place. This process is labor intensive and thus not a cost effective manner for manufacturing the door.
The honeycomb core fully extends between the horizontal rails and vertical stiles to completely fill the hollow interior. Consequently, more core material is inserted within the interior of the door than is actually required for support. The extra core material increases the cost of the door.
The honeycomb core has also been routed out in places to fit over the panels of molded doors. Such a honeycomb version failed because it was not possible to control the spread of members or strips since some of the members or strips would get caught or hung up on the top of the panels. Also, over expansion of the honeycomb core was hard to control.
Another type of door reinforcement includes solid blocks placed strategically between the door skins. The solid blocks are commonly formed of laminated strips of corrugated or from pieces of styrofoam. The use of multiple pieces of strips or blocks laid in the doors takes more set up time and requires a large quantity of material which is expensive. Also, these solid blocks require a significant amount of glue to be spread over their entire surface to bond to outer skins of the door.
The outer skins of hollow core doors maybe formed using a planar flush panel or they may have contoured colonial-type molded panel configuration. In a colonial-type panel configuration, a portion of the panel extends within the hollow interior of the door. The thickness of the hollow space in that area is reduced. Inserting a honeycomb structure or core in such a door is undesirable since the honeycomb core would have to be reduced in thickness in the areas where the panel extends within the hollow interior of the door.
It is therefore desirable to provide a structural to provide a structural core or support for a hollow core door which requires less set-up time and is cost effective by being easy to manufacture and by using a reduced amount of core material and glue.